The objectives of this program are to study the role of both behavioral and pharmacological variables in drug discrimination processes and to determine the effects of both acute and chronic drug interactions on complex behavioral processes. The baseline schedule of reinforcement maintaining responding will be varied in drug discrimination experiments to compare stimulus control under different schedules of reinforcement and to bias responding toward or away from making the drug response. Response bias and discrimination sensitivity will be analyzed by signal detection and analysis. Attempts will be made to compare drug effects on exteroceptive stimulus control with effects of the same drugs on interoceptive stimulus control exerted by the training drug in drug discrimination experiments. We will also attempt to establish drug discrimination without errors to compare stimulus control with this procedure with that under traditional training methods. The training drugs in drug discrimination experiments will include phencyclidine, opioid drugs, Delta9-tetrahydrocannabinol, cocaine and benzodiazepines. Of particular interest will be drug interaction studies to determine how one drug modifies the stimulus control exerted by another drug. Interactions among Delta9-tetrahydrocannabinol, cocaine, morphine and diazepam will be emphasized. In experiments on drug effects on complex behavioral baselines, behavior will be maintained under delayed matching-to-sample, single alternation, temporally spaced responding, repeated acquisition and fixed-consecutive number schedules. The effects of acute and chronic drug administration on these baselines will be determined. The same drugs and drug combinations used in the drug discrimination experiments will be emphasized. These experiments should provide valuable information as to how both pharmacological and behavioral variables influence the stimulus control exerted by drugs which, in turn, contributes to both drug abuse and non-compliance problems. The experiments on complex behavior should provide clues as to the consequences of drug taking on specific behavioral processes.